The present invention relates to the use of sulfonic acids as catalysts in resinous compositions.
Resinous compositions which are cured with aminoplast curing agents generally use an acid catalyst. A substantial number of acid catalysts are known and have been conventionally utilized such as boric acid, phosphoric acid, and a variety of sulfonic acids, for example, paratoluenesulfonic acid and methanesulfonic acid and disulfonic acids such as dinonylnaphthalene disulfonic acid and benzene disulfonic acid. U.S. Pat. Nos. 2,631,138, 2,961,424, 3,474,054, 3,979,478, and 4,083,830 describe such catalysts.
Although effective for the majority of uses, many of the known sulfonic and disulfonic acid catalysts have limitations, in particular applications. For instance, these materials often contribute to impaired humidity resistance in some coating compositions. There is therefore a need for a strong acid catalyst which will not only provide a rapid, effective cure at a moderate temperature, but also provide improved humidity resistance.